LEDs used as light sources in fiber optic communications must be precisely aligned to the device carrier, so that the optical emission from the device may be accurately directed into an optical communications fiber. Currently available LEDs with output suitable for use in optical communications have bonding pads on opposite surfaces. This structure has presented difficulties in mass producing optical devices that require alignment between LED and fiber, as explained in the Detailed Description below.
This alignment problem has sometimes been addressed by attaching the LED to an intermediate mounting which is subsequently attached to a base member and optically aligned to a fiber connector using an active alignment technique.
U.S. Pat. No. 5,337,398, which is assigned to the assignee of the present invention, and is hereby incorporated by reference, discloses an optical package utilizing solder bump self-alignment of the LED. That optical package has a base member provided with a plurality of bond pads sites for the self alignment as well as the electrical connection of an LED device directly to the base member. In addition, the base member has associated mechanical fiducials for the alignment of other optical mounting components: a spherical lens holder and a fiber ferrule receptacle. In this way, all the optical components are passively aligned when they are attached to the base member, and no subsequent alignment operation is required.